Friction Torque Characteristics and Design Optimization of Small Crossed Roller Bearings
Published on:
2026-01-16 16:49
Due to their compact size, excellent operational stability, high rotational accuracy, and rigid structure, small crossed roller bearings are widely applied in machine tool rotary tables, medical imaging equipment, industrial robotic arms, and rotating modules of precision detection devices. These components often undergo frequent start-stop cycles, making it critical to study their friction torque characteristics to enhance performance and longevity.
Research Background
In recent years, research on crossed roller bearings has primarily focused on:
Bearing fault diagnosis
Manufacturing process optimization
Raceway roundness error influence
Negative clearance effects on stiffness
However, there is limited study on the friction torque behavior of miniature crossed roller bearings, especially under complex load conditions such as overturning moments.
This article develops a mechanical model that considers raceway angle deviations and validates it experimentally to investigate how radial clearance, raceway angle deviation, and roller profiling affect bearing friction torque. The goal is to provide practical guidance for designing low-friction, high-precision bearings.
Methodology
A mechanical equilibrium model and a friction torque analysis model were established, incorporating:
Raceway angle deviation
Radial clearance
Roller profile shapes
These were evaluated through experiments using a small crossed roller bearing mounted in a working turntable subjected to overturning moments.
Key Findings and Analysis
1. Friction Torque Increases with Rotational Speed and Overturning Moment
The friction torque of small crossed roller bearings rises with increasing rotational speed and overturning load. In practical applications such as machine tool turntables, it's crucial to optimize operating conditions to prevent excessive friction and wear.
2. Effect of Radial Clearance on Friction Torque
Under a constant load:
A larger overturning moment results in higher friction torque.
As radial clearance increases, the friction torque decreases.
Beyond 5 μm, the reduction in friction torque stabilizes.
Recommendation: Keep radial clearance within 5–10 μm to balance stability and low friction.
3. Raceway Angle Deviations Increase Load Unevenness
The greater the raceway angle deviation, the more uneven the load distribution on the rollers, leading to:
Increased contact pressure
Higher friction torque
Recommendation:
Control inner raceway deviation within ±2′ (arcminutes)
Control outer raceway deviation within ±1′
4. Logarithmic Roller Profiles Reduce Friction Torque
Comparing roller profiles:
Logarithmically profiled rollers offer lower friction torque across various loading conditions.
When overturning moment nears 400 N·m, the difference between logarithmic and arc-shaped profiles becomes negligible.
Recommendation: Use logarithmic roller profiles in applications seeking minimum friction torque.
5. Sensitivity Analysis of Structural Parameters
From most to least influential on friction torque, the structural parameters are:
Radial clearance
Inner raceway angle deviation
Upper outer ring raceway angle deviation
Lower outer ring raceway angle deviation
Design Priority:
First control radial clearance
Then minimize inner raceway deviation
Followed by outer raceway angle tolerances
Design Recommendations
To achieve optimal friction torque performance in small crossed roller bearings:
Maintain radial clearance between 5–10 μm
Limit inner raceway deviation to ±2′
Use logarithmically profiled rollers
Carefully manage outer raceway machining tolerances
Conclusion
This study enhances the understanding of friction torque characteristics in small crossed roller bearings. By analyzing the effects of radial clearance, raceway angle deviation, and roller profiling, we provide practical design and application guidelines. These recommendations are essential for improving performance, efficiency, and durability in precision systems like robotic arms, medical equipment, and rotary tables.
Frequently Asked Questions
Q1: What factors most affect friction torque in small crossed roller bearings?
A: Radial clearance has the most significant impact, followed by inner raceway angle deviation.
Q2: How can I reduce friction torque in a high-load application?
A: Use logarithmically profiled rollers and maintain raceway angle deviations within recommended tolerances.
Q3: What is the ideal radial clearance range?
A: Between 5–10 μm for optimal stability and low friction.
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